isoniazid (Nydrazid, Laniazid, INH are all discontinued brands)

Omudhome Ogbru, PharmD

Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

GENERIC NAME: Isoniazid

DISCONTINUED BRANDS: Nydrazid, Laniazid, INH

DRUG CLASS AND MECHANISM: Isoniazid is an anti-bacterial drug that has
been used to prevent and to treat tuberculosis since 1952. Tuberculosis is an
infectious disease caused by a bacterium. Once the infection is acquired, it
usually remains dormant in the lungs for up to many years. Later, the infection
may become active in the lungs and sometimes spreads throughout the body.
Patients with a tuberculosis skin test that has recently become abnormal
(demonstrating recent infection with tuberculosis) but a normal chest X-ray
(demonstrating inactive infection) are given Isoniazid alone for 9 months.
Patients with active infection on chest X-ray are given Isoniazid combined with
other antituberculous drugs. The mechanism of action of Isoniazid is not known,
but it is thought to work through its effects on lipids (fats) and DNA within
the tuberculosis bacterium. It is very selective for the tuberculosis bacteria,
that is, it has few if any effects on other bacteria.

PRESCRIBED FOR: Isoniazid is used to prevent active tuberculosis in
persons who have an abnormal skin test for tuberculosis (latent tuberculosis) or
in combination with other drugs for the treatment of active tuberculosis.

SIDE EFFECTS: When Isoniazid is broken down by the liver, one of the
products is acetylhydrazine, a potent toxin for the liver. When taken over a
long period of time at standard doses, Isoniazid can cause important and even
fatal liver injury (hepatitis) in approximately 1 out of every 100 patients.
Isoniazid-associated hepatitis usually occurs during the first three months of
treatment but can occur at any time during therapy or even many months after
starting treatment. Elevated blood liver tests occur in between 1 in 20 and 1 in
10 patients. Usually, enzyme levels return to normal despite continuation of the
isoniazid, but in some cases progressive liver damage and even death occurs.